Inventory control and identification method

ABSTRACT

An inventory control and identification apparatus uses a storage space with a plurality of inventory items. Identification labels are positioned in physical correspondence with the inventory items. Each of the identification labels provides a transceiver. A coordinate communications network of further transceivers is set in a fixed position relative to the storage space and is enabled for wireless communication with the identification labels. A data processor is enabled for wireless communication with the coordinate network and the identification labels so as to receive data from the labels and the network. Inventory items have RF ID tags. Interrogation by the labels enables the tags to emit codes identifying the presence and location of the inventory to the labels. Triangulation of signals transmitted by the labels enables location of the labels in three-space.

RELATED APPLICATIONS

This is a continuation-in-part application of a prior filed andcurrently pending application having Ser. No. 10/304,671 and file dateof Nov. 25, 2002 now U.S. Pat. No. 6,736,316.

INCORPORATION BY REFERENCE

Applicant(s) hereby incorporate herein by reference, any and all U.S.patents, U.S. patent applications, and other documents and printedmatter cited or referred to in this application.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to inventory identification and controlsystems and more particularly to a system using inventory identitylabels mounted adjacent to inventory items, the labels providingidentification information relative to the inventory and wherein thelabels are enabled for communication with tags on the inventory itemsand with a computerized inventory management system, and wherein theinventory location, quantity and status is known at any time from aremote location.

2. Description of Related Art

The following art defines the present state of this field:

Neumark, U.S. Pat. No. 6,550,674 describes an inventory control andmanagement method providing a combination mobile device forcommunication and for reading labels (R&C). The R&C reads an inventorylabel affixed to an item of inventory in the stores. A data file iscreated corresponding to the label reading and includes a time stamptaken at the time of the reading. The data file is imported into acomputer data processor. A network of fixed distributed communicationnodes (transceivers) is positioned over the inventory store forreceiving temporal cyclic signature pulses from the R&C. At least threeof the communication nodes are used to perform a triangulation forlocating the R&C, and the location and the corresponding time isrecorded. By comparing the time of a given reading of the label with acorresponding time of the triangulation, it is possible to determinewhere any item is located within the stores.

Barritz et al, U.S. 2002/0,008,621 describes a system and method whichallows the identity of assets and their physical locations to be mappedand associated with one another. The invention includes a locator toolwhich receives an input which allows the tool to determine its ownspatial location and thereby the spatial locations of various objectssuch as furniture, computer equipment, and structural components such asdoors, windows to be identified and located and thereafter mapped in theform of architectural layout, diagrams, and the like. The invention isalso an inventory system as well as a verification system that allowsobjects or assets to be inventoried, tracked, or verified againstpurchasing lists or the like.

Goodwin, III, U.S. Pat. No. 5,794,215 describes a method of optimizingelectronic price label (EPL) systems which employs a three-dimensionalgraph of retry levels in a transaction establishment. The methodincludes the steps of determining locations of EPLs within thetransaction establishment, determining locations of transmit and receiveantennas that are used by a computer to communicate with the EPLs,determining retry levels for the EPLs, mapping the retry levels tolocations within the transaction establishment, producing athree-dimensional graph of the retry levels within the area of thetransaction establishment, and determining, from the graph, sub areaswithin the area having retry levels above a predetermined maximum retrylevel. Once the sub areas having higher retry levels are determined, thelocations of the transmit and receive antennas may be changed and/orinterfering structures may be moved until the retry levels of the subareas are below the predetermined maximum retry level.

DeTemple et al., U.S. Pat. No. 5,995,015 describes a system forcommunicating between a store computer and locations in the les of aretail facility. A hard-wired grid connects the store computer to aplurality of transceivers located in zones throughout the facility andthe transceivers establish a wireless link to the locations. Oneembodiment is a product information display system in which thelocations are fixed information display terminals, such as pricedisplaying shelf tags. Another embodiment is an item tracking system, inwhich the locations are movable shopping carts or baskets.

Failing, Jr. et al., U.S. Pat. No. 6,016,481 describes an improvedsystem for space management in retail stores. The space managementsystem includes price display labels mounted on rails along the edges ofshelves in a store. A communications link between the computer and thelabels permits the computer to address each label by a logical addressand to determine the physical location of each label to within aresolution of typically four feet. The system prepares price audit listsand adjacency audit lists that permit economical use of the time ofstore personnel during the audit. The lists are generated in such a waythat the items on a particular list are physically contiguous; thus oncethe correct general area has been located by the auditor littleadditional time need be spent locating the individual items. Inperforming an audit of product facings, the user is able to use thedisplay hardware, including the pushbutton on each label, as a datacollection system for product facing information. In product locationmode, the user starts at the first label at one end of a shelf andpresses the button on the first label. The user moves to the secondlabel, presses its button, moves to the third label, and the process isrepeated for each label along the shelf, and for the rest of the shelvesin the area being audited. This permits the system to collectinformation as to the sequence of labels along a rail.

Halperin et al., U.S. Pat. No. 6,105,004 describes a product monitoringsystem for monitoring a variety of products grouped according to theiridentities on shelves, including a central computer storing theidentification of each group of products on the shelves; a plurality ofelectronic shelf labels, each located adjacent to a shelf for a group ofproducts, communicating with the central computer, storing theidentification of the respective group of products, displayinginformation relating to the respective group of products, and readingout the identification of the respective group of products; a pluralityof portable units each to be carried by a user of the system; and arecord memory for each portable unit. Each portable unit includes aread-in device capable of establishing a short-range communication linkwith the read-out device of each electronic shelf label for reading inthe product identification and for recording same in the record memoryfor the respective portable unit.

Sutherland, U.S. Pat. No. 6,253,190 describes a shelf tag comprising aliquid crystal display having optical states which are stable withoutpower and an interface that allows for each character element to beprogrammed easily by sweeping a programming device across the characterelement contacts with all power and signal requirements being suppliedto the shelf tag by the programming device. The programming device canbe integrated with a portable transaction computer equipped with a barcode reader or can be embodied in a stand-alone apparatus capable ofreceiving user input, displaying information and interfacing to theshelf tags. A method of using the shelf tags, the programming device anda radio frequency computer local area network are presented whichautomates many typical business applications such as inventory updatingand simultaneously changing prices advertised on the shelf tags.

Brick et al., U.S. Pat. No. 6,269,342 describes an electronic pricingand display system using programmable electronic shelf tags.Programmable electronic shelf tags are used in connection with apparatusfor programming the electronic shelf tags. Pricing and productinformation is stored in databases of a computer system for suchpurposes as inventory control and updating pricing information. Aportable programming device is used to transmit programming data Methodsare provided for fast and convenient modification of large numbers ofelectronic shelf tags located throughout a facility (e.g., a retailstore).

Gelbman, U.S. 2001/0,020,935 A1 describes smart and dumb implementationsof a stand-alone, remotely updateable, remotely alterable, flexibleelectronic label. The electronic label provides for displayinginformation in connection with a mammal, non-mammal, an item orlocation. The label includes a display assembly having electronic inkdisposed on a support, one or more antennas for sending or receivingsignals corresponding to one of instructions, programs, data or selectedindicia to be displayed by said display assembly, a storage element incircuit with the antenna for storing the instructions, programs, dataand indicia, and one or more processors for intelligently determiningthe indicia to be displayed by the display assembly, for controlling andcoordinating operation of the label, and for generating output signalsfor instructing the display assembly to display the indicia.

Hook et al., U.S. 2001/0,054,005 A1 describes an electronic display tagsystem. The system has an electronic display tag including a display fordisplaying at least one of pricing data and product identification data,the display having bistable character elements or bistable pixels. Thedisplay tag has a decoder logic unit for decoding received programmingdata and for updating the display based on the programming data, theprogramming data being received wirelessly. The display tag also has awireless transceiver, the wireless transceiver for converting apower-inducing signal transmitted wirelessly to the display tag intoelectrical power, the electrical power used by the decoder logic unit toupdate the display.

Visible Tech-Knowledgy, LLC, WO 02/063602 describes smart and dumbimplementation of a stand-alone, remotely updateable, remotelyalterable, flexible electronic label. The flexibility of the electroniclabel allows the label to fit into and conform to the shape of themolding used in retail store shelving to display merchandize andwarehouse shelving. The flexible, thin label includes a flexible displayassembly having electronic ink disposed on a support, one or moreantennas for sending or receiving signals corresponding to one ofinstructions, programs, data or selected indicia to be displayed by thedisplay assembly, a storage element in circuit with the antenna forstoring the instructions, programs, data and indicia, and one or moreprocessors for intelligently determining the indicia to be displayed bythe display assembly, for controlling and coordinating operation of thelabel, and for generating output signals for instructing the displayassembly to display the indicia.

The prior art teaches a smart electronic label employing electronic ink,a programmable shelf tagging system, a method of optimizing electronicprice label systems, a remote electronic information display system forretail facilities, a space management system for retail stores, aproduct monitoring system, a programmable shelf tag and method forchanging and updating shelf tag information, and a programmable shelftag and method for changing and updating shelf tag information. However,the prior art does not teach a smart label with two-way radiocommunication capability for use in a three-space locating system. Thepresent invention fulfills these needs and provides further relatedadvantages as described in the following summary.

SUMMARY OF THE INVENTION

The present invention teaches certain benefits in construction and usewhich give rise to the objectives described below.

The present invention uses a network of ultra wide band (UWB) unitscapable, as a group, of precisely locating objects in three-dimensionalspace as described in U.S. Pat. Nos. 6,400,754 and 6,385,268 to Fleming,and U.S. Pat. No. 6,300,903 to Richards. These “units” are able todetermine their locations in reference to a give point in space.Miniature units may be built into electronic shelf labels as will bedescribed below. Once activated, these Units become part of a UWBnetwork. Such networks may comprise a wired or wireless simplex or fullduplex electronic labeling system and is advantageously employed instores and retail establishments. Each Unit is attached to an individuallabel; has its own address and the label displays data received from asource such as a computer system. Typically such information willinclude any of: description of an item, unit price, price per weightunit, quantity in stock, special promotions, etc. In duplex systems thelabel responds with an acknowledgement when addressed.

The primary purpose of the present invention is to incorporate theinformation displayed in such an electronic labeling system with theability to determine the accurate location of each label and to providean interactive data storage capability, that includes not only the datadisplayed by the label but also its location. This enables a virtual mapof a storage facility such as a retail store and provides significantadvantages. A further purpose of the present invention is to identifythe quantity of each item in storage upon interrogation.

Such a system reduces the stocking process cycle time, cuts down on newstore setup-time, improves stocking issues such as over or understocking, and enables users to locate a specific stock item quickly. Foron line shoppers, or from a store kiosk, locating items is very easy.

Transceivers are matched to labels and attached to shelves to identifyspecific stock items. The transceivers communicate so as to determinecurrent location, as described in the prior art. Each label displaysinformation pertaining to a specific stock item. Communication with thecomputer system to update the database with current location is easilyaccomplished. Such updates can be performed on a regular schedule, whena unit detects a change in its location or per user request when tryingto locate a specific item.

All physical fixtures, i.e. shelves, hooks, displays etc. are mapped asto exact size and location in the database. This results in the abilityto create a “virtual” store layout.

The present invention is an inventory control and identification systemand method for use in large inventory stores such as warehouses andretail establishments containing thousands of items. Such items may beof any type, such as automobiles, tires, hardware, tools, foodstuffs,and so on, and may be stored in a two-dimensional array, such as withautomobiles on a sales lot, or in a three-dimensional array (inthree-space) such as in aisles having racks.

A primary objective of the present invention is to provide a system andmethod of use that provides advantages not taught by the prior art.

Another objective is to provide such an invention capable of recordingthe nature, quantity and location in three-space, of items in aninventory stores.

A still further objective is to provide such an invention capable ofconfirming status of inventory remotely and with high accuracy.

Other features and advantages of the present invention will becomeapparent from the following more detailed description, taken inconjunction with the accompanying drawings, which illustrate, by way ofexample, the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings illustrate the present invention. In suchdrawings:

FIG. 1 is a conceptual diagram of the preferred embodiment of theinvention;

FIG. 2 is a perspective view of an information label of the invention;

FIG. 3 is a top plan view of a portion of a retail product having aconventional label with bar-code identifier and which is shown tocorrespond to the label of FIG. 2;

FIG. 4 is a perspective view of the retail product on a shelf with theinformation labels mounted on the front of the shelf;

FIG. 5 is a data processor computer display showing stocked itemlocations in accordance with the invention; and

FIG. 6 is a logic flow diagram illustrating the method of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

The above described drawing figures illustrate the invention in at leastone of its preferred embodiments, which is further defined in detail inthe following description.

The present invention is a system and method for the identification ofinventory stocks wherein the location and identity of any stock may bedetermined and its identity tag changed; all from a remote location. Thesystem is also able to determine how much inventory is held at eachlocation, shelf or bin, and transmit such information to data storage.The system uses a storage space 10, such as a warehouse, a supermarket,a parking garage, and a dead storage facility, and may be plural storagespaces 10 within a building, for instance, such as on different floors,or may even be in separate facilities. The storage space 10 receives aplurality of inventory items 20 (stock) such as packages, foodcontainers, vehicles and discarded obsolete equipments; and may be anyother type of item or item groups that are able to be sorted, stockedand identified. Storage space identification labels 30, referred tothroughout as simply “labels,” are preferably rectangular in shape, butmay be any shape, with a front display face 32 and a means for mounting34, such as the track engagement device shown in FIG. 2, and as is wellknown in the supermarket industry. The mounting means 34 engages areceiver 36, such as the track shown in FIG. 4. The labels 30 arepositioned in physical correspondence with the inventory items 20. Eachof the labels 30 provides a label tranceiving means 40 such as aminiature wireless radio frequency receiver and transmitter, as is wellknown in the art, and a presentation means 50 such as an electronicpictorial display, as for instance, a liquid crystal display, also wellknown in the art. The presentation means 50 appears on the front displayface 32 of the label 30. This is clearly shown in FIG. 2.

A coordinate communication network provides a means for networktranceiving 60 and is particularly comprised of plural radio frequencyreceivers and transmitters with UWB tranceiving capability, and ismounted in a fixed position and orientation relative to the storagespace 10. The network tranceiving means 60 is enabled for wirelesscommunication with the label tranceiving means 40, and also with a dataprocessing means such as a computer system 50, which is enabled for waveenergy signal communication with both the label tranceiving means 40 andnetwork tranceiving means 60. The display face 32 is enabled forpresenting pictorial representations of the inventory items 20 such asdescriptions related to the inventory items, to provide identificationand selection thereof. See FIG. 2.

In use, the system transmits wireless signals from the data processingmeans 50 to the label tranceiving means 40; the signals correspondingto, and causing the pictorial representations of the inventory items tobe displayed. Signals are sent, on demand, from the label tranceivingmeans 40 to the data processing means 50 to confirm satisfactoryoperation of the identification labels as well as the specificinformation being displayed. The labels 30 are located in 3-spacethrough a triangulation method using the coordinate network 60 as willbe described in detail below.

To accomplish its objectives, communication in the present inventiontransmits digital information over relatively short distances, asallowed by FCC rules, employing a well known digital wirelesscommunication technique as described in the prior art. Particularly,this wireless transmission of information is accomplished using lowpower, ultra wide band (UWB) communication signals which areparticularly suitable in the present application, as will be shown.Other communication protocols that are well known in communicationengineering could be used in place of UWB, but as stated, UWB hasparticular application here. Such communicating apparatus is so wellknown as to be easily duplicated in the present invention by those ofskill in the art and is fully described in the incorporated references.

A common need in inventory management is to determine the nature oridentity of inventory items and also their location, and the presentmethods can accomplish this economically and efficiently. A data file ordatabase 52 is established in the computer system 50, and this filecorresponds to the information displayed by labels 30. This step isknown, for instance, in the supermarket and grocery trade, each time anitem is scanned at a checkout counter, its identity is recorded in adata file, which is then imported into a database and the current knowninventory count of the item is reduced by one. Similarly here, the datafile is transmitted by wireless communication, as described above andshown in FIG. 1, from the labels 30 to the computer system 50. In likemanner, triangulation data signals are preferably sent by wirelessmeans, or wire means 62 to the computer system where label 30 locationinformation is then stored as records. Such a record, beside locationinformation, will contain information such as, item description, itemserial or stocking number, item count or quantity, item date, and so on.The record also contains the date and time of day that the reading tookplace. The data base may contain hundreds, or many hundreds of suchrecords, and the means for creating such a database and of importinginformation, such as described here, is very well known in the art.

The coordinate network 60 is a plurality of fixed distributedcommunication nodes positioned over or near the inventory items 20. Eachof the communication nodes, as previously described, is preferably anelectrical signal unit device with antenna, capable of both receivingand transmitting wireless electrical signals. Such devices are extremelyinexpensive when employed for low power and limited range applications.The number of nodes required in the present method will depend upon thesize of the inventory stores, the output power, signal to noise ratio inthe communication channel space, and other factors well known tocommunications engineers. Physically, the nodes may be mounted on orfrom a ceiling of a warehouse, or other building structure, or may bemounted on a network of wires strung or hung from a ceiling or frompoles in an indoor or out of doors stores and this is well known in theart. In the preferred embodiment, shown in FIG. 1, the nodes arewireless transceivers interconnected by electrical conductors 62 forsharing information. The wireless transmitted signals are able to useultra low power, being transmitted at roughly four orders of magnitudebelow typical output power rating for conventional RF transmissions. Byprecisely timing these transmissions, and by using matched antennas atthe nodes, highly efficient communication is possible, as is describedin the references. Because a wide spectrum is used, the UWB technique isonly able to be employed locally to avoid interference with commoncarriers. On the other hand, such UWB signals are typically immune tolocal interference which takes up only a small portion of spectrum. Asstated, the UWB signals are received by any of the nodes that are withinrange of a signal. Location information contained in the UWB signals issent to the computer system 70 where such information from at leastthree nodes, enables the determination of the location of specificlabels 30 in three-space through triangulation technique. In oneembodiment, the triangulation method for locating the labels 30 usesdiscrimination of received time of the signature signals to determinelocation. This approach requires that the clocks of the nodes aresynchronized.

The process proceeds as follows: the computer system 50 transmits alocation request signal with a label identification code. All of thelabels 30 receive this request signal. The label 30 that corresponds tothe identification code responds by transmitted a short burst signalcontaining the label's identification code and a time stamp, i.e., timeof transmission. All other labels 30 do not respond. Each of the fixednodes that are within range of the responding label 30 receives thelabel's signal burst and upon receipt time stamp the burst. The label'sand the node's time stamps are then transmitted to the computer system50 for computation. Since the exact locations of the nodes is known, andthe time of flight of the label's signal burst is able to be easilycalculated from the time stamps, the exact location in 3-space of thelabel 30 is calculated. Since the entire process takes on the order of atens of microseconds, a complete inventory of thousand of labels 30 maybe located in a few seconds.

As an example of this triangulation technique, the location of label 30(any one of the many labels in the apparatus) is determined when label30 is caused to emit a short burst of energy, e, at time t⁰. This burstis in response to a signal request from the computer system 50. Theburst, e, carrying its signature, “id”, is received by at least threenodes 1, 2 and 3 (second transceiver means 60) whose locations areexactly defined in the inventory space. The instant in time that thenodes receive e is identified, i.e., the nodes have clocks on board andthe instant a signal is received is noted by such clocks, the time beingattached digitally to the signature of the signal received. In thepresent case, the receipt times are t¹′, t² and t³ respectively.Assuming that the three nodes are at different distances from the label30, these three times will be distinct. The computer system 50 may notknow that e was emitted depending on the ability of receiver 54 to pickup this low energy signal. However, since the burst e contains the timestamp t⁰ each of the three nodes is able to read the initial time stampand transmit, by cables 62: t⁰ t¹ and t⁰ t² and t⁰ t³ to the computersystem 50. Since the velocity of propagation, v, of the signals throughspace is known, the distance of the label 30 from each of the nodes iscalculated as: d¹=v/t¹−t⁰ and d²=v/t²−t⁰ and d³=v/t³−t⁰. Now, bydefining circles about nodes 1, 2 and 3 with radiuses equal to d¹, d²and d³ respectively, the location of label 30 is known by the point ofintersection of the circles. This calculation is easily carried out onthe computer system 50 as is well known in the art and is highlyaccurate.

Alternately, the triangulation method may use signal directiondiscrimination of the signature signals to determine location. Thisapproach uses antenna systems that are able to distinguish within smalltolerances, the direction from which a signal is received and is wellknown in the art. Again a triangulation is accomplished from label'sburst signal. The foregoing discussion uses equipment, parts andtechniques that are well known in the art.

The present invention makes it possible to access the currentinformation presented by any of many thousands of labels 30, makechanges to the label's display or shut the label off.

The present method further comprises the step of composing a pictorialmap 100, as shown in FIG. 5, of the inventory items in the storagespace, as derived from the calculated locations of the labels 30. Suchcomputer graphic maps are well known in the art. The method furthercomprises the step of identifying any one of the labels 30 on thepictorial map by an indication as shown in FIG. 5 at column “D,” line 3,on the map 100. Such a map may be printed, as shown in FIG. 1, andplaced for use by employees, customers, etc.

From the above description it is seen that the present inventory controland identification apparatus includes plural storage spaces such as thatshown in FIG. 4, where each of the plural storage spaces engages atleast one inventory item 20 and preferably more than one. The a storagespace identification label 38 is positioned adjacent to each of thestorage spaces, and each said storage space identification labelprovides the label tranceiving means 40. As shown in FIG. 1, the meansfor network tranceiving established as an ultra-wide band coordinatecommunication network in a fixed position relative to the storagespaces. The label tranceiving means 40, the network tranceiving meansand the means for data processing 50 is established for mutual waveenergy communication. Each inventory item 20 provides a radio frequencyidentification tag 30 enabled for emitting a wireless identitytransmission upon exposure to a wireless radio frequency interrogationtransmission from label tranceiving means 40, or from a remotetransmitter (not shown). The method of this invention comprises emittingradio frequency interrogation transmissions from the storage space'slabel tranceiving means 40, preferably one at a time, receiving, at thelabel tranceiving means 40, a wireless identity transmission from eachone of the radio frequency identification tags 25 which are positionedon each one of the plurality of inventory items 20, and then determininginventory quantities and locations from the wireless identitytransmissions. As previously defined, triangulation locates the storagespace identification labels 30 using the coordinate communicationnetwork. Inventory is updated as to quantity and location in thedatabase of the data processing means 50. Clearly, the inventory itemtags 25 may be enabled for transmitting an identity specific code sothat the label tranceiving means 40 will receive only transmissions frominventory associated with each specific label tranceiving means 40. Thisis easily accomplished by simple signal filtering. Also, the distancebetween a given label tranceiving means 40 and its associated inventorytags 25 is easily computed by identifying the time between the emittingof the interrogation signal and the receipt of the several identitytransmission responses.

In FIG. 6 is illustrated a logic flow of the method of the presentinvention. From top to bottom, we see that a request is received byeither wireless or communication line method; the request is updated andsent via a smart label RF ID reader via wireless to interrogate RF IDtags or labels on inventory. An external reader may be used, i.e.,remote from the shelf labels 38 and powered by utility current. Theinventory tags respond and these responses are received by the RF IDreader, whereupon time stamp information, tag quantity information andshelf label location information to sent to the computer system 50 fordata processing and updating of its database.

While the invention has been described with reference to at least onepreferred embodiment, it is to be clearly understood by those skilled inthe art that the invention is not limited thereto. Rather, the scope ofthe invention is to be interpreted only in conjunction with the appendedclaims.

1. An inventory control and identification apparatus comprising: pluralstorage spaces, each holding at least one inventory item; each of theinventory items providing a radio frequency identification tag enabledfor emitting a wireless identity transmission in response to an energysignal; each of the storage spaces further engaging an identificationlabel having a label means for transceiving enabled for receiving theidentity transmission of the associated identification tags and fortransmitting time stamped label transmissions; a coordinatecommunication network having plural network means for transceiving andarranged in fixed positions relative to the storage spaces; and a meansfor data processing; the means for label transceiving, the means fornetwork transceiving and the means for data processing enabled formutual wave energy communication; the coordinate communication networkenabled for receiving the time stamped label transmission at, at leastthree of the network means for transceiving and for identifying a timeof receipt thereof; the data processing means enabled for receiving thetransmitting and receipt times of the time stamped transmissions and forcalculating locations and inventory quantities of the storage spaces byapplying a triangulation method.
 2. An inventory control andidentification method comprising the steps of: placing inventory items,having radio frequency identification tags in a plurality of storagespaces; engaging, on each of the storage spaces, an identification labelhaving a label means for transceiving enabled for receiving the identitytransmission of the associated identification tags and further enabledfor transmitting time stamped label transmissions; forming mutual waveenergy communication between the means for label transceiving, adistributed means for network transceiving and a means for dataprocessing; time stamping transmissions from the label means fortransceiving; time stamping a time of receipt of the label transmissionsat each of at least three points in the network transceiving means; andcalculating locations of the inventory items by applying a triangulationmethod using the means for data processing.